To Convert Textbox String to Byte Array

in the below code i need to get get the encoded value from textbox and need to convert it to byte array and then decrypt..

how can i do that

1. Dim xmlKeys As String 'A combination of both the public and
   'private keys

Dim xmlPublicKey As String 'The public key only

'The plaintext message in a byte array
Dim PlainTextBArray As Byte ()
'The cyphertext message in a byte array
Dim CypherTextBArray As Byte ()
<LI>In the Form_Load event, create both the public and private keys: Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load 'This creates both the public and the private keys Dim rsa As New RSACryptoServiceProvider 'Hold both keys in a global variable that will be used in the
'decryption procedure xmlKeys = rsa.ToXmlString(True) 'Hold the public key to be used in the encryption procedure xmlPublicKey = rsa.ToXmlString(False) End Sub<LI>Type in the procedures that encrypt and decrypt, respectively: Private Sub encrypt() Dim rsa As New RSACryptoServiceProvider 'get the public key so you can encrypt the message: rsa.FromXmlString(xmlPublicKey) 'get the message Dim message As String = TextBox1.Text If message.Length > 58 Then MsgBox("You must use fewer than
59 characters") : Exit Sub 'transform message string into a byte array: PlainTextBArray = (New UnicodeEncoding).GetBytes(message) ' Encrypt CypherTextBArray = rsa.Encrypt(PlainTextBArray, False) 'view the cyphertext in TextBox2: TextBox2.Clear() For i As Integer = 0 To CypherTextBArray.Length - 1 TextBox2.Text &= Chr(CypherTextBArray(i)) Next i 'see the lengths of the plaintext, and the cyphertext Me.Text = "Plaintext Length (Unicode): " & PlainTextBArray.Length
& " Cyphertext Length: " & CypherTextBArray.Length End Sub Private Sub decrypt() Dim rsa As New RSACryptoServiceProvider 'get the keys, thereby creating an RSA object that's identical ' to the one used in the Form_Load event when the keys were first built rsa.FromXmlString(xmlKeys) 'create a byte array and then put the decrypted plaintext into it Dim RestoredPlainText As Byte () = rsa.Decrypt(CypherTextBArray, False) 'Step through the two-byte unicode plaintext, displaying the restored
'plaintext message For i As Integer = 0 To (RestoredPlainText.Length - 1) Step 2 TextBox3.Text &= Chr(RestoredPlainText(i)) Next i End SubTrigger the procedures by button clicks:

Private Sub Button1_Click(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles Button1.Click encrypt() End Sub Private Sub Button2_Click(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles Button2.Click decrypt() End Sub